Solution structure of the [2Fe-2S]-ferredoxin from the halophilic archaeon Halobacterium salinarium

Corresponding publications:
B.-L. Marg, K. Schweimer, H. Sticht, D. Oesterhelt: A Two-Helical Extra Domain Mediates the Halophilic Character of a Plant Type Ferredoxin from the Archaeon Halobacterium salinarum. Biochemistry 44, 29-39 (2005)
Schweimer K, Marg BL, Oesterhelt D, Rosch P, Sticht H. (2000). Sequence-specific 1H, 13C and 15N resonance assignments and secondary structure of [2Fe-2S] ferredoxin from Halobacterium salinarum. Journal of Biomolecular NMR 16, 347-348.

Halophilic archaea are microorganisms that require 3-5 molar of salt for a proper lifestyle. The genome of H. salinarium encodes for a [2Fe-2S]-ferredoxin with a molecular weight of about 13 kD. The structure of the protein was solved by NMR methods in collaboration with Heinrich Sticht (University of Bayreuth).
The overall fold of the proteins shows an αβ-fold with five β-strands (β1-β5) and five α-helices (α1-α5) in an β2-β1-β4-β3-β5 architecture. β1 and β4 are parallel whereas β2, β3 and β5 are antiparallel β-sheets.
The core domain of the archaeal ferredoxin resembles the fold of ferredoxins known from plants including the 3-dimensional arrangement of cystein residues ligating the Fe-cluster. However a striking difference to all known plant structures appears through the presence of additional domain located at the N-terminal part of the protein (residues 6-38). This domain - predominantly α-helical in structure - comprises an unusual high number of negatively charged residues (in particular aspartates) and was supposed to express one of the most significant molecular determinants of bacterial halophilism [1].

Fig. 1: Structure of the H. salinarium Ferredoxin. The structure is contoured from the N-terminus (blue) to the C-terminus (red) and the iron-sulphur cluster is shown in grey-yellow. The figures were prepared using Molscript [2].

References

  1. B.-L. Marg, K. Schweimer, H. Sticht, D. Oesterhelt: A Two-Helical Extra Domain Mediates the Halophilic Character of a Plant Type Ferredoxin from the Archaeon Halobacterium salinarum. Biochemistry 44, 29-39 (2005)

  2. Schweimer K, Marg BL, Oesterhelt D, Rosch P, Sticht H. (2000). Sequence-specific 1H, 13C and 15N resonance assignments and secondary structure of [2Fe-2S] ferredoxin from Halobacterium salinarum. Journal of Biomolecular NMR 16, 347-348.

  3. Kraulis P.J., Domaille P.J., Campbell-Burk S.L., Van Aken T., & Laue E.D. (1994). Solution structure and dynamics of Ras p21.GDP determined by heteronuclear three- and four-dimensional NMR spectroscopy. Biochemistry 33, 3515-3531.

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